Method and apparatus for extracting pure water



Sept. 1, 1959 L. J. SCHMERZLER 2,902,414

METHOD AND APPARATUS FOR EXTRACTING PURE WATER Filed Oct. 16, 1957 I3 HEAT HUMID\F|ER HUM\D\F'IER FAN EXCHANGER 2 f AIR g F I2.

H I3 I! HEAT E CHANG-E J; I X R /l7 i 'I 1 HUMIDIF'IER II HEAT |5 I ExcuANeeR c SEPARATOR 6 j 5 AIR la WATER GRAINS 0F MO|STUE PER LB. OF DRY AIR.

DRY BULB TEMP. DEfir- F.

* LAWRENCE J.SCHMERZLER INVENTOR. FIG. 2.

BYM

United States Patent METHOD AND APPARATUS FOR EXTRACTING PURE WATER Lawrence J. Schmerzler, Bloomfield, NJ.

Application October 16, 1957, Serial No. 690,583

8 Claims. (Cl. 292-46) This invention relates to a method and apparatus which have for their object the economical extraction of pure Water from impure water by utilizing air characterized by a relatively high temperature and low moisture content.

Ideally therefore, the invention is most economically carried out in hot and dry areas where such air is readily available. However, limitation to these areas is not intended since a source of hot and dry air may be economically available in other areas, for example, as a by-prodnet in a power plant.

Prior methods and apparatus for reclaiming water operate on the basic principle of saturating air with water vapor and then condensing this water vapor out of the air. It is known that this condensed water vapor will be pure to the extent that it is usable for drinking purposes, even though evaporated from a source which is biologically, organically, or inorganically impure or contaminated.

The method and apparatus of the present invention likewise operate on this basic principle. However, they are distinguished from the prior art in that they are more economical in practice than the prior art methods and apparatus now used.

More particularly, in the present invention is is an object to utilize the hot and dry ambient air characteristic of various sections of this country, and thus available at no cost, to effect the saturation and condensation of pure water from air.

It has been found that because of the natural propensity of hot and dry air to readily absorb moisture, that after saturation, psychometric temperature changes can be readily induced in this air, and afterwards two circulated streams of the air passed in heat exchange relationship with each other to effect condensation of pure water from one of the air streams.

More particularly, the method of the present invention contemplates the use of hot and dry atmospheric air divided into two interacting streams. One of these is a temperature control stream and follows one path through the apparatus, and the other is a water vapor or moisture carrier stream and follows another path through the apparatus. It is the function of the control stream to supply the thermal head required for all heat transfer processes with the carrier stream and as a result induce the carrier stream to yield pure and drinkable water. Accordingly, all heat transfer operations occur internally between the two streams and no external source of heat is required.

The method of the present invention may be practiced utilizing any one of several well known types of heat exchangers, and for this reason no one particular unit is described in detail herein. On the other hand, the more eflicient the heat exchanger, the greater the yield of pure and drinkable water. For this reason, it is preferred to use a heat exchanger through which the air streams pass counterfiow rather than parallel flow, since such a heat exchanger is known to provide efficiency of vention, or maximum theoretical efficiency is as-v sumed for each heat exchanger in order to greatly simplify the calculation of the temperatures of the air streams, it being understod that while these temperatures cannot actually be attained, they are nevertheless realistic in view of the high operating efficiency of known counterfiow heat exchangers.

The invention will be better understod when considered in connection with the accompanying specification and drawings forming a part thereof, in which:

Figure 1 is a diagrammatic representation of the apparatus or" the invention in which the flow path of the circulated air streams are also illustrated.

Figure 2 is a graph of the temperature and moisture content of the air streams throughout their flow through the apparatus of Figure 1.

The apparatus In Figure 1, conduits or other suitable flow passage means are diagrammatically represented by the lines 10 and 11, which lines also serve to indicate the path of flow of the circulated air streams through. the apparatus shown. The air is circulated through these said conduits by the fans 12, likewise shown diagrammatically, situated at the inlet of each of the conduits. Downstream of the fans 12 the conduits it and 11 have suitable connections to the elements of apparatus also shown diagrammatically and labeled either humidifier" or heat exchanger.

It is proposed that each of the humidifiers 13, 13a, 14 and 15 be a well known type of apparatus which connected to a source of raw or impure water (not shown) is adapted to continuously spray the raw water onto a rotating matrix in contact with the air streams circulating through the conduits 1t) and 11 so that the air streams becomes saturated with water vapor. Likewise, each of the heat exchangers 16, 17 and 18 is to be a well known type of apparatus which is adapted to permit heat transfer between the air streams passing through it in counterflow relationship. Since structurewise these types of apparatus are well known in the prior art, they are not shown in detail in Figure l. The separator 19 is likewise a well known type of apparatus, such as an electrostatic precipitator, which is adapted to induce the precipitation of water vapor from air, and thus is not shown in detail in Figure l.

The direction of How of the carrier and control air stream through each of the conduits l0 and 11 respectively is indicated by the arrows by the fans 12. Through conduit 10, the carrier stream proceeds from the point designated 1 to the point designated 6. Through the conduit 11, the sequence of flow of the control stream is from the point also designated 1 to the point designated e. Thus during flow of the carrier and control air streams through each conduit, the heat exchanger 16 is the first heat exchanger encountered. In this respect, in conduit 10 the humidifiers l3 and 14 are connected on opposite sides of this first encountered heat exchanger 16, and the conduit then terminates through the heat exchangers l7 and 18. In conduit 11, the first encountered humidifier 13a is connected after the heat exchanger 16, and the conduit terminates through the Patented Sept. 1, 1959 The method To better understand the effect of the humidifiers and the heat exchangers on the circulating carrier and control air streams, attention is directed to the graph of Figure 2. In this graph, the numerals 1 through 6 and theletters a through e correspond to the like references shown in Figure 1, and thus the temperature and moisture content of the respective carrier and controlair streams may be observed on this graph at each of these selected points.

Thus, at point 1, or upon entry into each of the conduits 10 and 11', both the carrier and control air streams are at the same temperature of 95 F. and have 45 grains of moisture per pound of dry air. Since the ambient air characteristic of the southwestern states of this country is commonly at this temperature and humidity, the supply of air for the invention when practiced within this area would entail no expense.

' The first change in the condition of the air occurs to the carrier air stream of conduit 10 when it passes through the raw water sprayer 13 and as a result absorbs from 45 to 92 grains of moisture and undergoes a psychometric temperature drop from the dry bulb temperature of 95 F. to the wet bulb temperature of 65 F. (see graph line 12). In this and the other raw Water sprayers or humidifiers 13a, 14 and 15, it is preferred to use water which is at the same temperature as the air stream passing through the humidifier thereby permitting adiabatic humidification to take place.

Thus, when the carrier and control air streams next pass through the heat exchanger 16, the control air stream of conduit 11 still being at 95 F., will lose some of its heat to the carrier air stream of conduit 10 (see the graph lines 23 and 1a). As a result of this heat transfer the temperature of the carrier air stream of conduit 10 is raised from 65 F. to 95 F. and its capacity to absorb additional moisture is accordingly increased.

The carrier and'control air streams are next passed through a humidifier, although for different purposes. In the case of the carrier air stream of conduit 10 it is passed through the humidifier 14 principally to absorb the additional moisture of from 92 to 125 grains, and the drop in temperature to the wet bulb temperature of 74 F. is incidental (see graph line 3-4). In the case. of the control air stream of conduit 11 it is passed through the humidifier 13a principally to lower its temperature from the dry bulb temperature of 65 F. to the wet bulb temperature of 54 F., and the absorption of moisture is incidental (see graph line a-b). I

After passage of the control and carrier air streams through the humidifiers 13a and 14 respectively, the control air stream of conduit 11 is at 54 F. while the carrier air stream of conduit 10 is at the higher temperature of 74 F. and is completely saturated with water vapor. Itwill thus be appreciated that when these air streams are passed in heat exchange relationship with each other, as is proposed in the final step of the method of the present invention, that some of the heat from the carrier air stream of conduit 10 will transharm the control air stream of conduit 11, and as a result of the heat loss from the saturated carrier air stream of conduit 10, pure water will condense out of, or precipitate from this said air' stream during passage through the separator 19.

This final heat transfer step may be accomplished in a single heat exchanger, but in the present invention, it is preferred to use the two heatexchangers 17 and 18. This particular arrangement is preferred Sim? t permits connecting the humidifier in the conduit 11 between the heat exchangers 18 and 17, and thereby permits lowering the temperature of the control air stream of this conduit at this point to insure a more efficient heat transfer between the air streams in the heat exchanger 17. In other words, after the control air stream of conduit 11 has emerged from the heat exchanger 18 at the temperature of 72 F. due to the heat absorbed therein, passage through the humidifier 15 will lower its temperature to 61 F. before it enters the heat exchanger 18 (see graph lines b-c and c-d).

The effect on the saturated carrier air stream of conduit 10 of passing through the heat exchangers 17 and 18, as previously stated, is a loss of some of its heat to the lower temperature control air stream of conduit 11. More particularly, with theoretical maximum heat transfer between the carrier and control air streams in the heat exchangers 17 and 18, the carrier air stream of conduit 10 will drop in temperature from 74 F. to 66-"v F. and thus readily precipitate approximately 42 grains of water per pound of dry air during passage through the separator 19 (see graph lines 45 and 56).

Thus, in the method and apparatus of the present invention, the utilization of hot and dry circulated streams of air as herein described, results in effective and economical extraction of pure water from a source that is impure without the need of any external source of heat.

It will be understood that the invention is not to be limited to. the specific steps of the method herein disclosed, or to the specific apparatus or arrangement of apparatus herein shown, but that wide modifications can be made in each within the invention as defined by the claims.

What is claimed is:

1. In a method of extracting pure water from raw water using two or more circulating streams of relatively hot and dry air comprising the steps of saturating a first air stream with water vapor and effecting a temperature drop therein, passing said first air stream in heat exchange. relationship with a second air stream and effecting a rise in temperature and increase in water vapor carrying capacity of said first air stream and a lowering in temperature of said second air stream, saturating the air streams with water Vapor to increase the water vapor content of said first air stream and further lowering the.

temperature of said second air stream, and thereafter passing the air streams in heat exchange relationship with each other whereby heat transfer from the first to the second air stream causes the precipitation of pure water from the first air stream.

2. In the method as claimed in claim 1 wherein the last named heat exchange step is accomplished in two successive passes between the air streams, and between these heat exchange passes the second air stream is saturated with water vapor to lower its temperature to. insure an effective heat transfer from the first air stream. during the last heat exchange pass of the second air stream.

3. In a method of extracting pure water from raw water in a relatively hot and dry climate by the heat exchange interaction of two or more circulated streams of ambient. air comprising the steps of saturating a first air stream with water vapor and effecting a dry to wet bulb temperature drop therein, passing said first air stream in heat exchange relationship with a second air stream and effecting a rise in temperature and increase in water vapor carrying. capacity of said first air stream and a lowering in temperature of said second air stream, saturating the air streams with watervapor to increase the water vapor content of said first air stream and to effect a dry to wet bulb temperature drop in said second air stream, and thereafter passing the air streams in heat exchange relationship with each other whereby heat transfer from the first to the second air stream causes. the precipitation of pure water from. the first air stream.v

4, In the method as claimed in. claim 3 wherein the last named heat exchange step is accomplished in two successive passes between the air streams, and between these heat exchange passes the second air stream is saturated with water vapor to lower its temperature to insure an effective heat transfer from the first air stream during the last heat exchange pass of the second air stream.

5. In the method as claimed in claim 4 wherein during the heat exchange steps the air streams are passed in counterflow relationship with each other to insure more efiicient heat transfer therebetween.

6. In a method of extracting pure water from raw water in a hot and dry climate in which a first circulated stream of ambient air is saturated with water vapor and subsequently the water vapor is condensed out of said air stream, the improvement in said method of using a second stream of ambient air to cause said condensation of water vapor comprising the steps of passing said second air stream in heat exchange relationship with the saturated first air stream to initially lower the temperature of said second air stream, subsequently saturating the second air stream with water vapor to further lower its temperature with respect to the saturated first air stream, and thereafter passing the air streams in heat exchange relationship with each other whereby the loss of heat from the saturated first air stream to said second air stream causes a precipitation of pure water from the first air stream.

7. In the method as claimed in claim 6 wherein the last named heat exchange step is accomplished in two successive passes between the air streams, and between these heat exchange passes the second air stream is saturated with water vapor to lower its temperature to insure an effective heat transfer from the first air stream during the last heat exchange pass of the second air stream.

8. An apparatus for extracting pure water from raw water including, a pair of spaced heat exchangers, two separate conduits connected between said heat exchangers and adapted to pass fluids in counterflow relationship with respect to each other through said heat exchangers, humidifiers in one of said conduits connected before and after the first encountered heat exchanger, humidifiers in the other conduit connected intermediate the heat exchangers, means for supplying raw water to said humidifiers, and means for forcing streams of relatively hot and dry air through said conduits whereby psychometric changes in the air stream in passing through the humidifiers and heat exchangers will result in the precipitation of pure water from the first named air stream.

References Cited in the file of this patent UNITED STATES PATENTS 2,761,292 Coanda et al. Sept. 4, 1956 

1. IN A METHOD OF EXTRACTING PURE WATER FROM RAW WATER USING TWO OR MORE CIRCULATING STREAMS OF RELATIVELY HOT AND DRY AIR COMPRISING THE STEP S OF SATURATING A FIRST AIR STREAM WITH WATER VAPOR AND EFFECTINGA TEMPERATURE DROP THEREIN, PASSING SAID FIRST AIR STREAM IN HEAT EXCHANGE RELATIONSHIP WITH A SECOND AIR STREAM AND EFFECTING A RISE IN TEMPERATURE AND INCREASE IN WATER VAPOR CARRYING CAPACITY OF SAID FIRST AIR STREAM AND A LOWERING IN TEMPERATURE OF SAID SECOND AIR STREAM, SATURATING THE AIR STREAMS WITH WATER VAPOR TO INCREASE THE WATER VAPOR CONTENT OF SAID FIRST AIR STREAM AND FURTHER LOWERING THE TEMPERATURE OF SAID SECOND AIR STREAM, AND THEREAFTER PASSING THE AIR STREAMS IN HEAT EXCHANGE RELATIONSHIP WITH EACH OTHER WHEREBY HEAT TRANSFER FROM THE FIRST TO THE SECOND AIR STREAM CAUSES THE PRECIPITATION OF PURE WATER FROM THE FIRST AIR STREAM. 